Cooler for rotary kiln

ABSTRACT

A plurality of material cooling tubes are attached in parallel alignment around the periphery of the material discharge end of a rotary kiln. An oblique passage is provided from each tube to the interior of the kiln for conducting air from the tube to the kiln. A first duct is provided for receiving hot material from the kiln. The first duct is within the oblique passage and extends from the kiln a predetermined distance to a terminal portion thereof intermediate the kiln and tube. A second duct is provided which has a first end portion connected to the terminal portion of the first duct and the second duct projects out of the oblique passage to be exposed to surrounding atmosphere. The second duct has a second end portion connected to the tube. The second duct is a spiral that turns away from the adjacent end of at least about 180* to where it discharges material into the tube and the tube projects through the space inwardly of the spiral duct toward the adjacent discharge end of the kiln. The spiral duct, being exposed to atmosphere, is cooled and material therein is cooled, to reduce thermal stress in the assembly.

United States Patent I McDonald [54] COOLER FOR ROTARY KILN Daniel McDonald, Beaconsfield, Quebec, Canada Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

[22] Filed: Nov. 5, 1970 [21] Appl.No.: 87,246

[72] Inventor:

[73] Assignee:

Primary Examiner-John .l. Camby AttorneyArthur M. Streich, Robert B. Benson and John P.

Hines Feb. 22, 1972 [57] ABSTRACT A plurality of material cooling tubes are attached in parallel alignment around the periphery of the material discharge end of a rotary kiln. An oblique passage is provided from each tube to the interior of the kiln for conducting air from the tube to the kiln. A first duct is provided for receiving hot material from the kiln. The first duct is within the oblique passage and extends from the kiln a predetermined distance to a terminal portion thereof intermediate the kiln and tube. A second duct is provided which has a first end portion connected to the terminal portion of the first duct and the second duct projects out of the oblique passage to be exposed to surrounding atmosphere. The second duct has a second end portion connected to the tube. The second duct is a spiral that turns away from the adjacent end of at least about 180 to where it discharges material into the tube and the tube projects through the space inwardly of the spiral duct toward the adjacent discharge end of the kiln. The spiral duct, being exposed to atmosphere, is cooled and material therein is cooled, to reduce thermal stress in the assembly.

4 Claims, 3 Drawing Figures COOLER r011 ROTARY KILN BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to rotary kilns and in particular coolers for generally horizontal or slightly inclined rotary kilns of the type disclosed in US. Pat. No. 828,555 granted to Paul O. Krottnaurer on Aug. 14, 1906 and U.S. Pat. No. 3,279,775 granted to Alexander J. Roubal on Oct. 18, 1966.

2. Description of the Prior Art In assemblies such as disclosed in the Krottnaurer U.S. Pat. No. 828,555, hot material was discharged through radially extending peripheral openings in the kiln into cooling tubes mounted in axially parallel alignment around the circumference of the discharge end of the kiln. These tubes rotate with the kiln around the central axis of the kiln and as each tube is carried through the lowest segment of its circular path a portion of the hot material in the kiln is discharged into each tube. Each tube is provided with internal spiral flights projecting inwardly from inner surface of the tube and as the kiln and cooler assembly rotate the spiral flights move the material from an inlet end of each tube, through the tubes and out a discharge end thereof. When material reaches the opposite end of a tube, from the charge end, the material is discharged into collecting or transporting devices as desired. As material moves through the tubes it is exposed to cooling air that is passed through the tubes in the direction opposite to material flow through the tubes. The counterflow of the air through material in the tubes cools the material and heats the air. The heated air passes into the kiln and provides preheated secondary air which combines with fuel and primary air from a nozzle to provide rapid combustion of fuel in the kiln.

A problem associated with assembly disclosed in the Krottnaurer patent was that the capacity of the cooling tubes was reduced by the fact that some of the material discharged from the kiln into each tube, as each tube passed through the lowest segment of its path of travel, fell back into the kiln as the tubes approached and passed through the highest segment of its path around the central axis of the kiln. For relatively heavy, dustless or large particle material this problem was substantially overcome by providing an oblique passage from the kiln to cooler tubes rather than the radial path shown in the Krottnaurer patent. For light, dusty or fine particle material the oblique passage was not as effective. When processing a very fine material such as alumina a still serious problem remained because undesirably dusty conditions have prevailed in the kiln. It is with this problem that the later patent to Roubal, U.S. Pat. No. 3,279,775 was concerned.

According to the Roubal patent the material flowing out of the kiln into the cooling tubes and the preheated air flowing out of the cooling tubes into the kiln are kept out of contact with each other. It had been determined that most of the dust pickup by the preheated air occurs near the air discharge end of the cooling tubes and in the passages connecting the tubes with the kiln. The material in the Roubal apparatus is kept out of contact with the air in this portion of the system by providing an enclosed duct within each passage connecting a cooling tube to the kiln. The duct for the material is of smaller crosssectional area than the remaining portion of the passage devoted to air passage. The entry to the duct is located at the upstream edge of a passage opening in the kiln so substantially all of the material drops into the duct and little or none of the material spills over into the air conveying portion of the passage where it can be picked up by the air and carried back into the kiln. Each enclosed duct extends from the port of the passage connecting the kiln to a tube, through the passage into the tube where the enclosed duct makes at least about 1% spiral turns around the inner surface of the tube before dumping material within the tube where the usual spiral flights will take over and move the material through the remaining length of the cooling tube. In some installations of that construction, however, high-thermal stresses have been experienced that resulted in severe cracking of welds that secure the spiral flights within the cooling tubes and the spiral flights themselves have burned away.

Other examples of prior art kilns, not including features of the present invention which will hereafter be described, are U.S. Pat. No. 2,904,322 of 1959, U.S. Pat. No. 3,372,915 of 1968 and British Pat. No. 83 l ,413 of 1960.

SUMMARY OF THE PRESENT INVENTION In a preferred embodiment of the present invention a plurality of material cooling tubes are attached in parallel alignment around the periphery of the material discharge end of a rotary kiln. An oblique passage is provided from each tube to the interior of the kiln for conducting air from the tube to the kiln. A first duct is provided for receiving hot material from the kiln. The first duct is within the oblique passage and extends from the kiln a predetermined distance to a terminal portion thereof intermediate the kiln and tube. A second duct is provided which has a first end portion connected to the terminal portion of the first duct and the second duct projects out of the oblique passage to be exposed to surrounding atmosphere. The second duct has a second end portion connected to the tube. The second duct is a spiral that turns away from the adjacent end of at least about to where it discharges material into the tube and the tube projects through the space inwardly of the spiral duct toward the adjacent discharge end of the kiln. The spiral duct, being exposed to atmosphere, is cooled and material therein is cooled, to reduce thermal stress in the assembly.

The invention will now be described in greater detail with reference to the drawings in which:

FIG. 1 is a partial end view of a kiln assembly according to the present invention, with various portions broken away;

FIG. 2 is a view taken along line 11-11 of FIG. 1 taken in the direction indicated by the arrows; and

FIG. 3 is a view taken along line III-III of FIG. 2 taken in the direction indicated by arrows.

Referring to FIG. 1 and FIG. 2, a rotary kiln assembly 10 comprises a cylindrical shell 1 l lined with refractory brick I2. The kiln assembly 10 is supported and driven by means (not shown) to turn as indicated by the arrow in FIG. 1. A plurality of port castings 13 project obliquely through shell 11 and lining 12 and open to the interior of the kiln I0. A plurality of material cooling and air preheating tubes 20 are arranged around the discharge end of the kiln 10 with a central axis through each of the tubes 20 being parallel with a central axis through kiln 10.

Structural means 21 are provided defining an oblique passage 22 from each tube 20 to the interior of kiln I0. Wall structure 23 defines a first duct 24 for receiving hot material from the kiln l0 and conducting the hot material away from the kiln 10. The wall structure 23 defines the first duct 24 within the oblique passage 22 and the first duct 24 extends from the kiln 10 a predetermined distance to define a terminal portion shown as flange 25 intermediate the kiln 10 and tube 20. Wall structure 26 is provided which defines a second duct 27 having a first end portion defined by a flange 28 which is connected to the flange 25, for receiving hot material from the first duct 24. The wall structure 26, which defines the second duct 27, projects out of and away from the structural means 21 which defines the oblique passage 22. The second duct 27 is provided with a second end portion 29 connected to the tube 20 for discharging the material from the kiln l0 and first duct 24 into the tube 20. The second duct 27 is a spiral that turns away from the discharge end of kiln 10. As shown in FIG. 3 the second duct 27, from flange 28 to end portion 29, turns about an axis 30 central of tube 20 at least about 180 to place end portion 29 on a side of tube 20 opposite flange 28. An end portion 20a of the tube 20, as shown in FIGS. 2 and 3, projects through the space inwardly of the spiral duct 27 and toward the adjacent discharge end of kiln 10. The spiral duct 27, from flange 28 to end portion 29, is exposed to surrounding atmospheric air and both the duct 27 and the material therein is cooled to reduce thermal stress caused by the material after it enters ducts 20 and makes contact with spiral flights 31 secured within tubes 20 by welds 32 (shown in FIG. 2).

In the operation of the described assembly hot material will advance through kiln toward the discharge end of the kiln and the port castings 13 as the kiln is rotated about its central axis in the direction indicated by an arrow in FIG. 1. As can be seen from FIG. 2, the hot material will spill over the upstream edge of castings l3 and drop into duct 24. Material entering duct 24 will pass through the portion of duct 24 in casting 13, then through the portion of duct 24 in the oblique passage 22 and then through the spiral duct 27 external of passage 22. The rotational motion of the entire assembly will move material through the spiral duct 27, out the end portion 29 and into tube 20. Thereafter material will be moved through tubes 20 by the flights 31 to the discharge ends of tubes 20 (not shown). Cooling air may be admitted into tubes 20 through the material discharge ends of the tubes by any conventional arrangement (not shown) which may be such as disclosed in the earlier mentioned Krottnaurer patent. The spiral duct 27, is exposed to atmosphere and cooled thereby, and does not therefore burn out, nor are welds damaged by overheating such as the welds 32 (FIG. 1) or welds (not shown) that may be utilized to fabricate sheet metal to make the ducts 27.

From the foregoing it will be understood that the present invention is possessed of unique advantages. However, such modifications and equivalents of the disclosed concepts such as readily occur to those skilled in the art are intended to be included within the scope of this invention and thus the scope of this invention is intended to be limited only by the scope of the claims such as are, or may hereafter be, appended hereto.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a rotary kiln assembly having a plurality of cooling tubes attached in parallel alignment around the periphery of the material discharge end of the kiln and having means defining an oblique passage from each tube to the interior of the kiln for conducting air from the tube to the kiln, the improvement comprising:

a. wall structure defining a first duct for receiving hot material from the kiln and conducting the hot material away from the kiln, the wall structure defining first duct being within the oblique passage means and extending from the kiln a predetermined distance to define a terminal portion of the first duct intermediate the kiln and the tube; and

b. wall structure defining a second duct having a first end portion connected to the terminal portion of the first duct for receiving hot material therefrom, the wall structure of defining the second duct projecting out of the oblique passage means from the terminal portion of the first duct and extending therefrom external of the oblique passage means and exposed to surrounding atmosphere, the second duct having a second end portion connected to the tube for discharging the material from the kiln and first duct into the tube with the second duct and the material therein being cooled by its exposure to surrounding atmosphere.

2. In a rotary kiln assembly according to claim 1, the second duct being of spiral configuration with the second end portion thereof discharging material into the tube at a location in a plane perpendicular to the kiln spaced a greater distance from the adjacent discharge end of the kiln than the first end portion of the second duct.

3. In a rotary kiln according to claim 2, the spiral configuration of the second duct extending at least about around an axis central of the tube.

4. In a rotary kiln according to claim 2 the tube having an end portion of reduced diameter projecting through a space defined inwardly of the spiral configuration of the second duct in an axial direction toward the adjacent discharge end of the kiln. 

1. In a rotary kiln assembly having a plurality of cooling tubes attached in parallel alignment around the periphery of the material discharge end of the kiln and having means defining an oblique passage from each tube to the interior of the kiln for conducting air from the tube to the kiln, the improvement comprising: a. wall structure defining a first duct for receiving hot material from the kiln and conducting the hot material away from the kiln, the wall structure defining first duct being within the oblique passage means and extending from the kiln a predetermined distance to define a terminal portion of the first duct intermediate the kiln and the tube; and b. wall structure defining a second duct having a first end portion connected to the terminal portion of the first duct for receiving hot material therefrom, the wall structure of defining the second duct projecting out of the oblique passage means from the terminal portion of the first duct and extending therefrom external of the oblique passage means and exposed to surrounding atmosphere, the second duct having a second end portion connected to the tube for discharging the material from the kiln and first duct into the tube with the second duct and the material therein being cooled by its exposure to surrounding atmosphere.
 2. In a rotary kiln assembly according to claim 1, the second duct being of spiral configuration with the second end portion thereof discharging material into the tube at a location in a plane perpendicular to the kiln spaced a greater distance from the adjacent discharge end of the kiln than the first end portion of the second duct.
 3. In a rotary kiln according to claim 2, the spiral configuration of the second duct extending at least about 180* around an axis central of the tube.
 4. In a rotary kiln according to claim 2 the tube having an end portion of reduced diameter projecting through a space defined inwardly of the spiral configuration of the second duct in an axial direction toward the adjacent discharge end of the kiln. 